Tilting at Asteroids

JimPooley writes "The European Space Agency are conducting a feasibility study into a future mission to knock an asteroid off course. A Spanish company are planning the 'Don Quixote' mission to launch a pair of spacecraft at an asteroid. One hits the asteroid, while the other monitors it to see what happens."

Comments

Cheaper, easier and

[PhysicsGenius]

more accurate to paint them white and let the sun do the work.

Same Thing we do Every Night

[medcalf]

Hidalgo and Sancho? Is anyone else humming "Mouse of La Mancha"?

I see a grey rock and I want it painted white...

[Mad Bad Rabbit]

Xilman writes:

To be serious: I'm not convinced its either cheaper or easier. If the impactor is nothing but a solid lump of metal with some terminal guidance on board that is going to be a lot cheaper and simpler than a robot big enough and smart enough to paint several square kilometers of asteroid surface. Admittedly, the observation probe has to be smarter and so more expensive.

The impactor could be flimsy drums of titanium oxide powder, with some terminal guidance on board and a self-destruct charge. A few hours before the probe hits the asteroid, ground control detonates the probe and turns it into a big cloud of white dust. This keeps going and hits the asteroid, coating the surface with reflective pigment.

>:K

Re:Typical

[Danse]

God can kiss my shiny metal ass if he thinks I'm in favor of just letting some rock smash into the planet and kill everything. Besides, if you believe in God, then it works in your favor either way. If the asteroid hits the earth, then it was God's will. If we destroy the asteroid, then it was just God testing us.

Re:This is worthwhile

[Ethidium]

The danger is there. The indefinite survival of the species requires dealing with it sometime. Yes, climate change, warfare, disease (AIDS, cancer, et al) are all threats to the survival of our species. So is asteroid impact. We don't know how immediate any of them are, so we had better get planning. Just because something doesn't happen often doesn't mean it won't happen soon.

500-Year floods happen about once every 500 years, right? Doesn't mean it didn't happen in 1993. "A few times every hundred million years" could mean tomorrow. Sky surveys are great, but they don't have the whole sky covered, nor will they in the near future. To quote a popular space-opera, "it's a big-ass sky."

Kicking it off course by a few mm takes 1000 years

[geoswan]

...If all goes to plan, the asteroid's orbit will be disturbed in the beginning by a few fractions of a millimetre...

I did some of the math for this, on the back of an envelope, when we were this asteroid story from late July.

That asteroid was thought to have something like one chance in 300,000 of hitting the Earth in 16 years. I chose 10 years as the amount of time it would take to get something out there to divert it. I assumed it was headed straight at the Earth's center. Then I asked myself how much of a nudge we would have to give the asteroid so it would no longer hit the Earth?

If an asteroid were headed right towards the Earth, we would have to give ti a big enough nudge to change its target by d-day by something like 5,000 kilometres. That is 5*10^9 millimetres. So if gave an asteroid that was going to hit Earth a nudge of one millimetre per second at right angles to its current trajectory, wouldn't it take at least 5*10^9 seconds to change a direct hit to a near miss?

There are only 3.1*10^7 seconds in a year.

So a course change of 1 mm per second will protect us if we have something like 150 years lead time. But adding in a safety margin, and considering they only plan to divert the asteroid fractions of a mm, then that sounds like at least 1000 years.

Re:Kicking it off course by a few mm takes 1000 ye

[Mt._Honkey]

This is only a test run. I imagine that if we were to actualy try to save the planet, we would hit it with a MUCH bigger satalite, moving MUCH faster. And paint it white. And maybe hit it with some nukes. Add it all up, and you'll get more than just that

In other news...

[Snafoo]

The European Space Agency has discovered that, when hit with a space ship at a high velocity, the asteroid can slow and be sucked into the gravity well of a nearby planet.

You have three minutes to call your parents one last time. Don't die lonely.

Costs of Asteroid diversion

[geoswan]

Oh yeah, some slashdotters were suggesting that if we were going to go to the trouble of diverting an asteroid, like 2002 NT7, so it didn't hit us, why didn't we go all the way, and divert it enough to capture it in a useful low earth orbit?

The simple answer is that would be a cost a lot more energy. 2002 NT7 would have hit Earth with a velocity of 28 km per second. Earth's escape velocity is 11 km per second. To divert it so it wouldn't hit earth required changing its velocity by something like 28 centimeters per second. Capturing it in LEO would require changing its velocity by close to 28 kilometers per second.

Those velocities differ by a factor of 10^5.

Now maybe my Physics is really rusty, but the formula for kinetic energy is one half mass times the square of the velocity. So, unless my physics is rusty, the energy to capture 2002 NT7 would be 10^10 times greater than just diverting it.

If we really needed a big pile of rock in LEO wouldn't we be better off just quarrying the moon?